First Report of Organochlorine Pesticides and Heavy Metals in a Stranded Bottlenose Dolphin Off the Central Coast of Veracruz State: A Warning to Assess Pollution in a Reef Marine Ecosystem from the Gulf of Mexico

Live-strandings of cetaceans are uncommon in the southwestern Gulf of Mexico. However, an adult female bottlenose dolphin (Tursiops truncatus) with normal body condition was recorded at Pelicano’s Beach on the coast of Veracruz State. Health assessment showed multiple external injuries, possibly caused by the stranding event, as well as potential bacterial infection, and, thus, the individual was held in temporary facilities for rehabilitation. Blood samples were taken to assess the health status of the individual and were also analyzed for concentrations of 20 pollutants (14 organochlorine pesticides [OCPs] and six heavy metals [HMs]). The animal was released and found dead within a few days. The concentration of OCPs and HMs were close or above the government limits. Although these were lower than those reported in other living, free-ranging bottlenose dolphins, there are well-known negative effects for health. Low OCP values were attributed to an offloading process through lactation or mobility of the lipophilic OCPs that pass from blood to fat. Whereas HM concentrations (mainly non-essential metals: mercury [Hg], lead [Pb], and cadmium [Cd]—2.73, 21.13, and 12.67 µg L-1, respectively) were probably linked to the diet and the possible distribution of the specimen (possibly offshore). This is the first report on pollutants from anthropogenic origin in the area where uncontrolled activities are of major concern within a protected national reef park. Since marine ecosystems are under continuous pressure, several health issues for top predators are being noticed; therefore, this study underlines the relevance of studying health status of marine mammals in the Mexican waters of the Gulf of Mexico.